Treatment of respiratory conditions

ABSTRACT

A device (102) provides respiratory treatment for SDB (including mild OSA) and other respiratory conditions. A flow generator warms and humidifies gas at controlled flow levels. For example, the device (102) delivers breathable gas to the upper airway at flow rates of about 10-35 Liters/minute. Levels of flow rate, temperature and/or humidification of the device may be automatically adjusted in response to the detection of SDB events. The device may also automatically deliver adjustments of any of the levels in accordance with detected phases of respiratory cycles. In some embodiments, the device automatically delivers distinct levels to either of the nares based on independent control of flow to each nare. A warm-up procedure controls temperature and humidity at a desired target during a ramp-up of flow to the set therapy level. A cool-down procedure controls temperature above the dewpoint to avoid condensation internal to the device and patient interface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing dates of U.S.Provisional Patent Application No. 61/059,084 filed Jun. 5, 2008 andU.S. Provisional Patent Application No. 61/117,375 filed Nov. 24, 2008,the disclosures of which are hereby incorporated herein by reference.

1. FIELD OF THE TECHNOLOGY

The present technology relates to methods and apparatus for treatment ofrespiratory conditions such as the conditions related to sleepdisordered breathing (SDB) (including mild obstructive sleep apnea(OSA)), allergy induced upper airway obstruction or early viralinfection of the upper airway.

2. BACKGROUND OF THE TECHNOLOGY

Sleep is important for good health. Frequent disturbances during sleepor sleep fragmentation can have severe consequences including day-timesleepiness (with the attendant possibility of motor-vehicle accidents),poor mentation, memory problems, depression and hypertension. Forexample, a person with nasal congestion may snore to a point that itdisturbs that person's ability to sleep. Similarly, people with SDB arealso likely to disturb their partner's sleep. One known effective formof treatment for patients with SDB is nasal continuous positive airwaypressure (nasal CPAP) applied by a blower (air pump or compressor) via aconnecting hose and patient interface. In some forms the supply of airat positive pressure is delivered to both the nose and mouth. Thepositive pressure can prevent a collapse of the patient's airway duringinspiration, thus preventing events such as snoring, apnoeas orhypopnoeas and their sequelae.

Such positive airway pressure may be delivered in many forms. Forexample, a positive pressure level may be maintained across theinspiratory and expiratory levels of the patient's breathing cycle at anapproximately constant level. Alternatively, pressure levels may beadjusted to change synchronously with the patient's breathing cycle. Forexample, pressure may be set at one level during inspiration and anotherlower level during expiration for patient comfort. Such a pressuretreatment system may be referred to as bi-level. Alternatively, thepressure levels may be continuously adjusted to smoothly change with thepatient's breathing cycle. A pressure setting during expiration lowerthan inspiration may generally be referred to as expiratory pressurerelief. An automatically adjusting device may increase the treatmentpressure in response to indications of partial or complete upper airwayobstruction. See U.S. Pat. Nos. 5,245,995; 6,398,739; 6,635,021;6,770,037; 7,004,908; 7,141,021; 6,363,933 and 5,704,345.

Other devices are known for providing respiratory tract therapy. Forexample, Schroeder et al. describes an apparatus for delivering heatedand humidified air to the respiratory tract of a human patient in U.S.Pat. No. 7,314,046, which was filed on 8 Dec. 2000 and assigned toVapotherm Inc. Similarly, Genger et al. discloses an anti-snoring devicewith a compressor and a nasal air cannula in U.S. Pat. No. 7,080,645,filed 21 Jul. 2003 and assigned to Seleon GmbH.

It may be desirable to develop further methods and devices for treatingupper respiratory conditions.

3. SUMMARY OF THE TECHNOLOGY

A first aspect of the some embodiments of the technology is to providemethods and apparatus for treatment of respiratory conditions.

Another aspect of some embodiments of the technology is to providemethods and apparatus for treating sleep disordered breathing.

In one embodiment of the technology, air at a high flow rate isdelivered to the nasal passages, preferably in the range of about 10 toabout 35 litres/minute.

In another embodiment, air is provided with a temperature in the rangeof about 30° C. to about 37° C.

In another embodiment, air with a high humidity is provided to the nasalpassages, preferably with an absolute humidity in the range of about 27to about 44 mg/litre.

In another embodiment, methods and apparatus are provided forservo-controlling sleep disordered breathing by varying one or more offlow, temperature and level of humidification.

Another aspect of the technology is to provide a device for treatingrespiratory conditions having one or more start-up and/or shut-downprotocols that vary any of flow, temperature and level ofhumidification. For example, the device may provide for ramping any oneor more of flow, temperature and level of humidification.

Another aspect of the technology is to vary any of flow, temperature andlevel of humidification within, or as a function of detection of, arespiratory cycle of a patient. For example, a device may provide firstlevels of flow, temperature and/or humidification during inhalation andsecond or different levels of flow, temperature and/or humidificationduring exhalation.

Another aspect of the technology is to provide different levels of flow,temperature and/or humidification to each naris. For example, in oneform of device, levels of flow, temperature and/or humidification arecycled between the nares.

In accordance with the technology, methods and apparatus are providedfor varying the levels of flow, temperature and/or humidification.

In accordance with the technology, levels of flow, temperature and/orhumidification may be varied either manually or automatically.

In accordance with the technology, levels of one or more of flow,temperature and humidification may be varied over a period having aduration less than, equal to or greater than the duration of arespiratory cycle. For example, flow, temperature and humidification maybe increased over several breaths, or decreased over several breaths.

Another aspect of the technology is to provide an air delivery conduithaving a diameter that changes along its length.

Another aspect of the technology is to provide each naris withindividually controlled levels of flow, temperature and/or humidity.

Additional features of the present respiratory technology will beapparent from a review of the following detailed discussion, drawingsand claims.

4. BRIEF DESCRIPTION OF DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

FIG. 1 shows example components of an apparatus for treatment of theupper airway of a patient;

FIGS. 2A and 2B illustrate embodiments of a gate valve for adjustingtemperature and/or humidity of the treatment provided by an apparatus ofthe present technology;

FIG. 3 shows a rechargeable embodiment of an apparatus for treatmentaccording to an embodiment of the present technology;

FIG. 4 shows an example decreasing airflow channel diameter of adelivery conduit for a flow source of the present technology;

FIG. 5 is an example flowchart describing the control of the apparatusin warm-up mode;

FIG. 6 is another example flowchart describing the control of theapparatus in warm-up mode;

FIG. 7 shows a flowchart describing the control of the apparatus incool-down mode;

FIG. 8 is an illustration of an embodiment of a patient interface withinternal nasal dilators for insertion within a patient's nares;

FIG. 9 is a side view illustration of another example embodiment of apatient interface with external nasal dilators for contact with anexternal surface of the patient's nose;

FIG. 10 is a top view illustration of the example patient interface ofFIG. 9;

FIG. 11 is a front cross-sectional view illustration of the examplepatient interface of FIG. 9;

FIG. 12 is an illustration of an example diffuser clip configured withan example disengagement sensor;

FIG. 13 is a further clip with another example disengagement sensor;

FIG. 14 illustrates an example diffuser for a prong of a nasal cannula;and

FIG. 15 is an illustration of a baffle for a prong of a nasal cannula.

5. DETAILED DESCRIPTION

The embodiments of the present technology may be implemented with anairway treatment device 102 that may include some or all of thecomponents illustrated in FIG. 1. For example, the airway treatmentdelivery device will typically include a flow generator such as aservo-controlled blower 104. The blower 104 will typically include anair inlet and impeller driven by a motor (not shown). Optionally, theair inlet may be coupled with a gas supply, such as for oxygen as shownin FIG. 1, to mix with or supplement the breathable gas supplied by theimpeller to the airway of a user. Optionally, the supplementary gassupply may be introduced through a port, 133, upstream of thehumidifier, and/or downstream of the humidifier, through a port 134.Moreover, an air filter may be provided, such as a HEPA filter, toremove dust or other allergens from the air drawn into the air inlet.The blower may optionally be configured for generating varied flows orpressures.

The delivered breathable gas flow rate may be in the range of about −250to about +250 liters/min, more preferably between about −100 and about100 liters/min, more preferably, between about 0 to 100 liters/min, morepreferably between about 0 and 75 liters/min, yet further morepreferably between about 0 to about 50 liters/min with the preferredrange being between about 10 to about 35 liters/min, to provide forcomfort and efficacy.

The delivered breathable gas temperature may be in the range of about−10° C. to about 50° C., more preferably about +4° C. to about +45° C.,yet more preferably room temperature up to 40° C. with the mostpreferred range being 30° C. to 37° C., to provide for comfort andefficacy.

The delivered breathable gas relative humidity may be in the range ofroom humidity up to 100%, for example in the range of about 50% to about100%, or about 70% to about 100%, or about 80% to about 95%, with thepreferred range being 90% to 100%, to provide for comfort and efficacy.An absolute humidity range will be about 0 to about 82 mg/liter, or morepreferably about 27 to about 44 mg/liter.

5.1 Patient Interface

The airway treatment device 102 will also typically include a patientinterface such as an air delivery conduit 106 and nasal prongs or nasalcannula 108 to carry the flow of air or breathable gas to the upperairway of a user of the device or patient. The blower 104 can be coupledwith the air delivery conduit 106 and the nasal cannula 108 so as toprovide the breathable gas from the blower 104. In one form of patientinterface, as will be discussed in more detail with respect to theparticular interface embodiments herein, exhaust gas of the blowerand/or expiratory gas from the patient's airway can be vented away fromthe patient interface from a location proximate to the patient's airwayor the nares themselves. Significant gaps or venting between the patientinterface and the nares of the patient can permit a flow from the flowgenerator to escape or leak from the patient's nares without beinginspired. A patient interface that permits such venting can provide acomfortable interface for the treatment described herein. Thus, apatient interface that provides a leak-free seal with the nares of thepatient is not required. However, a sealed patient interface may be usedas an alternative.

The patient interface will typically be held in place proximate orinside the nares of the patient. A harness 110 may be optionallyprovided for this purpose. In addition, a nasal or septum clip and/oradhesive (not shown) may also be provided to maintain the nasal cannulain a desired position for use. Examples of suitable embodiments of thepatient interface are disclosed in U.S. Patent Provisional PatentApplication No. 61/058,659, entitled “Unobtrusive Interface Systems,”filed on Jun. 4, 2008, the disclosure of which is hereby incorporatedherein by cross-reference. In some embodiments, the nasal cannula mayalso or alternatively include ear attachment portions connected with thenasal cannula to ensure positioning of nasal cannula by or in the naresduring treatment. For example, cannula arms extending over and/or aroundthe ears from the nasal cannula may be utilized. Optionally, thedelivery conduit may be incorporated with such cannula arms, which mayalternatively be designed to run under the ears rather than over theears to reduce noise that might otherwise be heard by the user from theflow of gas through the delivery conduit.

In some embodiments, the patient interface or cannula may be implementedwith a nasal dilator, such as an internal or external nasal dilator.Illustrations of example embodiments are shown in FIGS. 8 to 11. In theembodiment of FIG. 8, dilator extension members 882R, 882L project froma patient interface such as a portion of a cannula 808 body. Forexample, the extension members may project from prongs 880R, 880L of thecannula 808 as illustrated in FIG. 8. In such a case, the prongs serveas dilator mount portion of the cannula or patient interface. Theextension members in FIG. 8 are sized to project inside nares of apatient's nose even if the prongs 880L, 880R also do not extend withinthe nares. Such extension members may then be formed or shaped to ply anexpansion force against an internal surface of each nare. This expansionforce, which is illustrated by the arrows in FIG. 8, permits theextension members to assist with keeping the nasal passages dilated frominside the nares. Thus, the extension members may be formed of amaterial that is flexible and resilient to provide a dilation force.However, these extensions may otherwise be configured with one or morespring elements (not shown) to provide a suitable expansion force withmore rigid extension members.

In some embodiments, the extension members of the patient interface maybe formed to ply an expansion force from an exterior surface of apatient's nares. An example of such an embodiment is illustrated inFIGS. 9-11. In such an embodiment, the extension members 982 maycomprise a dilator strip or strips. For example, a portion of thepatient interface or cannula 908 may include a bridge support 990. Thebridge support may be flexible for adjustment so that it may conform tothe nose shapes of different patients. When the cannula is in place toprovide gas flow to the nares of a patient, the bridge support mayextend from the cannula so that the bridge support is proximate to aridge area of a patient's nose. The support may then serve as a dilatormount portion to permit the dilator extension members to be mountedthereto and positioned proximate to the exterior surface of thepatient's nose.

For example, the bridge support 990 may optionally include a gap or clipso that a disposable dilator strip may be releasably retained by thebridge support 990. In such an embodiment, a disposable dilator stripmay be inserted or coupled to the bridge support for use. Such a dilatorstrip may then be a flexible and resilient material so as to permitplacement at opposing external surfaces of the nose of the patient andyet still be able to ply the expansion force at those surfaces to assistwith dilation of the nares by pulling at the exterior surfaces of thenose. Thus, these strips may also typically include an adhesive so thata surface of the dilator strip may adhere to opposing exterior surfacesof the nose. Thus, a left side dilator strip 982L and a right sidedilator strip 982R may then be adhered to the left and right sides ofthe patient's nose respectively. With such embodiments, the extensionmembers may serve the purpose of securing the cannula or patientinterface in a suitable position for providing a flow to the nares ofthe patient with prongs 980, 980R, 9080L as well as providing a dilationforce to assist with keeping the patients nasal passages open during ause of the patient interface. Moreover, although not shown in FIGS.8-11, additional components of the patient interface may be provided forfurther securing of the cannula in the desired position for use, such asthe cannula arms previously discussed.

In some embodiments, the extension members 982L, 982R may be morepermanently constructed with the bridge support by, for example, formingthe dilator strip as an incorporated portion of the patient interface orbridge support of the cannula 908. Thus, rather than replacingdisposable exterior dilator strips as previously discussed, for each usea suitable adhesive may be re-applied to the nasal surface sides of theattached or incorporated dilator strip.

In some embodiments, an optional spring element 996 may also be providedwith the dilator strip. For example, where extension members themselvesare not formed to have a sufficient resilience to provide the expansionforce, the spring element, when coupled with the extension members, mayserve to provide the expansion force with the extension members 992R,992L. In the example of FIG. 9, a wire or other resilient component mayserve as the spring element.

As further illustrated in FIG. 9, the patient interface may also includeone or more swivels. A swivel 994 can permit the patient interface orcannula 908 to remain in a desirable position for directing the flow tothe nares of the patient if a patient moves during sleep. Thus, a swivelprovides relative movement between an air delivery portion of thepatient interface and a delivery tube portion of the patient interface.For example, one or more swivels may permit relative rotation between acannula 908 and delivery tube 906 about one or more different axes(illustrated as perpendicular axes X, Y, Z). As illustrated in theembodiment of FIG. 9, a swivel may permit a rotation of the cannula 908with respect to the delivery tube 906 along arrows S1 or about animaginary X axis. Such movement can permit an air delivery portion ofthe cannula (e.g., prongs 980) to vertically rotate with respect to thedelivery tube 906.

Similarly, as illustrated in the embodiment of FIG. 10, a swivel 994 maypermit a rotation of the cannula 908 with respect to the delivery tube906 along arrows S2 or about an imaginary Y axis. Such movement canpermit an air delivery portion of the cannula (e.g., prongs 980L, 980R)to horizontally rotate with respect to the delivery tube 906.

Finally, as illustrated in the embodiment of FIG. 11, a swivel maypermit a rotation of the cannula 908 with respect to the delivery tube906 along arrows S3 or about an imaginary Z axis. Such movement canpermit an air delivery portion of the cannula (e.g., prongs 980L, 980R)to tilt rotation with respect to the delivery tube 906.

5.2 Humidifier, Heater and Tube

Breathable gas is supplied to the patient by a blower (104 of FIG. 1),which may be integrated with other elements of the apparatus, or from areticulated source, or from bottled gas, or otherwise. The air may befiltered at the input to the blower (104) or at some other point in thegas flow path. Optionally, the apparatus may also include a humidifierand/or heater (112, 111) and a delivery tube heater (135) (or apparatusto regulate heat loss from the delivery tube 106). In the case of aheated delivery tube, insulation material may be provided on the tube toprevent the heat from the tube from bothering the patient or otherwisebeing transferred to the skin of the patient. Such a tube may be wrappedwith an insulating material or the tube material may be selected for isinsulation properties. For example, the delivery tube may be increasedin thickness to provide or increase its insulating effect. The heaterdevice 111 may be exposed to a water mass and/or to the breathable gasflow. For example, the humidifier device may include a reservoir orfluid circuit for passing the breathable gas through or proximate with afluid or vapor of the reservoir or fluid circuit. One or more heatingelements (not shown separately from heater 111) may be provided to warmthe fluid to create the vapor and/or to warm the breathable gas byconvection. The warming device may further include a pump forcirculating fluid within the reservoir or a fluid circuit of the patientinterface or blower. For purposes of regulating the temperature and/orhumidity of the warming element, the apparatus may also include humiditysensors (117, 121, 134), and/or temperature sensors, and/or a flow ratesensor, and/or pressure sensors. The sensor(s) generate temperatureand/or humidity signals and/or a flow rate signal, and/or pressuresignals (illustrated in FIG. 1) for controlling the humidifier and/orheater and/or tube heater using control logic (120) to maintain thetemperature and/or humidity of the breathable gas delivered to thepatient. In some applications, this device can be controlled to alterthe temperature and humidity of the breathable gas such that thedelivery conditions are within the acceptable or preferred ranges asstated above.

Generally, it has been found that some available devices are slow whenchanging the level or degree of humidification due to the need to heat arelatively large mass or water. However, in embodiments of the presenttechnology, two air streams may be provided, namely a first relativelydry air stream in one flow channel, and a second relatively moist airstream in another flow channel. By mixing the streams to a third flowchannel, the level of humidification of the air delivered to the patientmay be rapidly changed as necessitated by the settings of the apparatus.

One means of achieving this is to employ an active flow gate 299 asillustrated in the examples of FIGS. 2A and 2B. For example, if FIG. 2A,when the flow gate is in one position, it directs flow from the blowerto a path that provides for one desired level of temperature andhumidification of the breathable gas, and in an alternate positiondirects flow from the blower to another path that provides asignificantly different level of temperature and humidification of thebreathable gas, optionally with no humidification. The flow gate may becontrolled to switch flow direction in response to breathing cyclephase, or otherwise under control of the controller 120. Optionally, theflow gate may be controlled to activate to a position that allows thesplitting or mixing of the flow between the two paths. For example,based on the desired humidity and/or temperature settings measured byone set of sensors in a combined tube, the controller may adjust theflow gate to mix variable amounts of gas of two distinct flow paths attwo different humidity and/or temperature settings, which may beseparately controlled by readings from two additional and different setsof sensors. Another version of the flow gate that allows for mixing offlows is illustrated in FIG. 2B with a controllable iris valve. Othermechanisms of generating and mixing flows of different temperatures andhumidities, such as dual blower supply, may be used.

By way of further example, by controlling the flow gate in conjunctionwith detected changes in the patient's respiratory cycle, a lowerhumidity and/or temperature gas may be delivered during patientexpiration and a higher humidity and/or temperature gas may be deliveredduring patient inhalation. Alternatively, a higher humidity and/ortemperature gas may be delivered during exhalation. Thus, such flowcontrol of the humidity of the breathable gas delivered to the patientcan generate high temperature and/or humidity delivery only when thepatient requires such for therapeutic reasons, for example during aninhalation phase of a breathing cycle. This controlled delivery in turnmay allow for a reduction in the power and/or water requirements of theapparatus over the duration of a therapy session. Detection of thephases of the respiratory cycle of the patient may be based on ananalysis of data from an appropriate sensor such as the sensorsdiscussed in more detail herein.

In one embodiment, shown in FIG. 4, the delivery conduit 406A, 406B,406C from the airway treatment device may be formed with a gas deliverychannel that has a decreasing cross section or diameter. A reduction inthe cross section diameter can reduce the impedance of the delivery tubeand may also reduce heat loss. For example, as illustrated in theembodiment of the delivery conduit of the open airway treatment device402 of FIG. 4, an internal airflow channel GC of the delivery conduitdecreases from at least one larger cross sectional area portion shown asdelivery conduit 406A to at least one smaller cross sectional areaportion shown as conduit 406B to a yet smaller cross sectional areaportion shown as delivery conduit 406C proximate to the nasal cannula408. In this way, for a given flow resistance, the tube diameterproximal to the patient can be smaller than with a constant diametertube. Further, the tube section 406A, and optionally 406B, may be heated(not shown) to control the breathable gas temperature and/or humidity toa level that allows for the change in temperature of the breathable gasthrough 406C such that the delivered gas to the patient is within thedesired range. The small tube section of 406C reduces the heat transferbetween the breathable gas and the environment compared with the largersections of 406B or 406C.

The cross sectional area of any portion of the airflow channel wouldtypically be smaller than the cross sectional area of the airflowchannel of the upstream portion of the delivery conduit. To avoidundesired flow restriction and/or noise, transitions between thesedifferent cross sectional portions of the delivery conduit may be madeby gradual blending at or near their intersections. Additional tubeportions may be interposed between 406A and 406B to provide for moregentle transitions in diameter.

In one embodiment, the end portion of the delivery conduit near the flowgenerator may have an internal airflow channel cross section diameter ofabout 8-15 mm. Such an embodiment may also end with an airflow channelhaving a cross sectional area diameter of about 3-6 mm proximate to thenasal cannula. Such a delivery conduit may optionally be formed as afoam silicone tube to provide improved thermal insulation properties.

5.3 Sensors

In some embodiments, the airway treatment delivery device may optionallyinclude one or more flow sensors 116. For example, flow through thenasal cannula 108 may be measured using a pneumotachograph anddifferential pressure transducer or similar device such as one employinga bundle of tubes or ducts to derive a flow signal. Although the flowsensor is illustrated in FIG. 1 in a location proximate to the blower,the flow sensor may optionally be located closer to the patient, such asin the patient interface or nasal cannula 108.

The airway treatment device may also optionally include one or morepressure sensors 114, 131, such as a pressure transducer. The pressuresensor(s) 114, 131 can be configured to measure the pressure generatedby the blower 104 and/or supplied at the nasal cannula or patientairway. In the illustrated embodiment, the pressure sensors 114, 131 areproximate to the blower and located downstream of the blower proximateto the patient interface. For example, one or more pressure sensors maybe located in the prongs or body of the nasal cannula. The pressuresensor(s) 114, 131 generates a pressure signal(s) indicative of themeasurement(s) of pressure at its particular location. Such a signal(s)can be utilized in settings or calculations of the device. The pressuresensor 114 has only been shown symbolically in FIG. 1 since it isunderstood that other configurations and other components may beimplemented to measure the pressure associated with the blower 104. Forexample, the pressure may be deduced from knowledge of the blowerperformance characteristics and the operating blower current and/orvoltage and/or rotational speed and/or flow rate. Optionally, differentgroups of sensors may be provided for a delivery tube associated witheach nare of the nasal cannula. For example, a delivery tube for eachnare may include a pressure sensor and/or flow sensor so thatindependent measurements of flow and/or pressure may be measured foreach nare.

The airway treatment device may also include one or more temperaturesensors as previously mentioned. For example, such sensors may belocated to measure the heater(s) 111, 135, and/or the treatment gas atvarious locations in the delivery tube such as near the blower (e.g.,before or after), after the humidifier and near the patient. Similarly,the treatment device may also include one or more humidity sensors asdescribed above. Thus, humidity may be measured before and/or after thehumidifier and near the patient. Additional such sensors may be employedwhen multiple flow channels are utilized such as in the embodiments ofFIGS. 2A and 2B for more measuring of the conditions of the distinctportions of the tubes. Still further sensors may also be configured tomeasure ambient humidity and temperature.

5.4 Controller

The signals from the various sensors (when present) may be sent to acontroller or processor 120. Optional analog-to-digital (A/D)converters/samplers (not shown separately) may be utilized in the eventthat supplied signals from the sensors are not in digital form and thecontroller is a digital controller. Based on input signals from thesesensors and/or other optional sensors, the controller may in turngenerate blower control signals. For example, the controller maygenerate an RPM request signal to control the speed of the blower 104 bysetting a desired frequency or rotational velocity set point andcomparing it with the measured condition of a frequency or velocitysensor. Alternatively, such changes may be based on determining adesired flow set point and comparing it with the measured condition ofthe flow sensor. Typically, such changes to the motor speed areaccomplished by increasing or decreasing supplied motor current with theservo based on determined differences between set and measuredconditions such as in a closed loop feedback fashion and translating thedifference to current. Thus, the processor 120 or controller may makecontrolled changes to the flow delivered to the patient interface by theblower 104. Optionally, such changes to flow may be implemented bycontrolling an exhaust with a mechanical release valve (not shown) toincrease or decrease the exhaust while maintaining a relatively constantblower speed.

The controller or processor 120 is typically configured and adapted toimplement particular control methodology such as the methods describedin more detail herein. Thus, the controller may include integratedchips, a memory and/or other control instruction, data or informationstorage medium. For example, programmed instructions encompassing such acontrol methodology may be coded on integrated chips in the circuits ormemory of the device or such instructions may be loaded as software orfirmware using an appropriate medium. With such a controller orprocessor, the apparatus can be used for many different open airwaytreatment therapies, such as the flow treatments previously mentioned,by adjusting a flow delivery equation that is used to set the speed ofthe blower or the exhaust venting by an optional release valve (notshown). Thus, flow may be set to desired levels as set by the switchesof the device and optionally increased in response to detectedrespiratory conditions such as an apnea, hypopnea, or airway resistance.The flow rate may be kept substantially constant over the phases ofrespiration. In some embodiments, the generated flow may be keptgenerally constant over the respiratory cycle and provide some endexpiratory relief. Alternately, in some embodiments the flow may bevaried smoothly to replicate the patient's detected respiration cycle.

In another example embodiment of the device, indications of upper airwayobstruction determined by the controller are servo-controlled by varyingthe flow rate and/or level of humidification and/or temperature. Forexample, a device in accordance with the technology monitors the patientfor signs of partial or complete upper airway obstruction. Upondetection of partial upper airway obstruction, and according to theseverity and frequency of such events, the level of humidification isincreased. In some embodiments, if the partial airway obstruction iseliminated, or not detected, the level of humidification may be reduced.Similarly, if partial airway obstruction is detected, flow may befurther increased.

In one embodiment of the technology, indications of the need to varytreatment are derived from a pressure signal that is in turn used toinfer patient flow in the controller 120. The inferred flow estimate isapplied to automatic pressure control algorithms such as those describedin U.S. Pat. No. 5,704,345, the entire contents of which are herebyexpressly incorporated by cross-reference. The output of the automaticpressure algorithms is however, in one embodiment, used to control theflow rate and/or level of humidification and/or temperature.

In other forms, pressure is used directly by the controller to determinethe presence of partial or complete airway obstruction. In other forms,other non-pressure, non-flow based diagnostic techniques are used, suchas movement of the suprasternal notch, patient movement, sympatheticnervous system activation (e.g. sweating, skin resistance, heart rate),pulse oximetry, EEG and ECG. Such additional diagnostic devices may beconfigured with the apparatus to provide measurement data to thecontroller.

In one embodiment, the controller may determine a tidal volume orinspired volume of air or gas by the patient during treatment. Such adetermination may be used for setting the pressure or flow and/oranalyzing conditions of the patient's airway or respiration. In view ofthe venting or unsealed nature of the patient interface that permits theexternal flow, the tidal volume (V_(P)) may be determined by measuringthe volume of air delivered by the blower (V_(O)) and measuring ordetermining the volume of leak air (V_(L)) associated with the nasalcannula and subtracting the latter from the former (e.g.,V_(O)−V_(L)=V_(P)). In some embodiments, the patient interface may sealwith the patient nares but have a pre-determined venting characteristic,or one that may change as a function of the pressure or flow ratesetting of the flow generator. Thus, the volume of leak may bedetermined by a look-up table or calculation by the controller 120 basedon the settings of the flow generator.

5.5 Other Aspects of the Apparatus

In other embodiments of the technology, the apparatus can be combinedwith additional components like accessories, which may be attached topre-defined interfaces or using the shape of the embodiment, openings,screw holes, or other coupling methods or prominent areas of theapparatus to attach. These accessories can be for example additionalfilters, or sound dampening mechanisms, or data logging electronics,which may have for example either a mechanical, pneumatic, magneticand/or electrical connection to the apparatus. The connection andinteraction may also be wired so that the accessories work together withthe apparatus from a distance.

One example is a chargeable battery pack as illustrated in FIG. 3. Theairway treatment device of this embodiment may be implemented with a DCbattery sufficient to permit at least a use for a single sleep sessionwithout connection to an AC power outlet. A dock 333, such as a cradlewith a docking port charger that may be releasably coupled with acharging port of the respiratory treatment device 302, provides aconvenient way to charge the battery of the respiratory treatment device302.

Other accessories can add additional features to the devices or modifythe existing feature set, for example by using a new method for motorcontrol to reduce noise. For example, a noise sensor or microphone maybe provided to detect levels of noise generated by the blower or thepatient interface. Noise measurements may be made and an increase inambient noise (e.g., a level of sound after filtering out frequenciessuch as the frequencies that may be associated with snoring) may beresponded to by the controller 120 changing a motor speed in attempt toreduce the noise. However, the controller may further reject suchchanges to the extent that any change would prevent a minimum desiredlevel of treatment from being generated by the flow generator for thepatient.

5.6 Warm-Up Methodology

One practical consideration in the design and operation of the apparatusdescribed herein is that the humidification apparatus may comprise anarrangement whereby a mass of water is required to be increased ordecreased in temperature. This, in turn, may result in some delaybetween the change in the heater state and the humidity and/ortemperature of the breathable gas delivered. When such a delay preventsthe desired combination of flow, temperature and humidity to be met inthe delivered gas, it may be desirable to prioritize the properties thatare to be met for therapeutic, comfort or functional reasons. Forexample, it may be desirable to ensure that humidity is within thepreferred range as the first priority, temperature is within thepreferred range as the second priority, and flow is within the preferredrange as the third priority.

Such prioritizing can be accomplished by the logic sequence described inFIG. 5. The flow rate Fmin is a small flow of about 5%-35% of thedesired therapy flow—sufficiently large to transport the breathable gasto allow sensing and control, but sufficiently small to ensure that thepatient does not suffer any discomfort as a consequence of the deliveredsub-optimal breathable gas.

Optionally, this sequence may be initiated conditionally upon, and/ortriggered by, detection of a patient connected to the apparatus. Suchdetection may be by observation or detection of fluctuations in pressureand/or flow signal(s) and other techniques such as those described inU.S. Pat. No. 6,240,921 (ResMed Limited), the contents of which arehereby expressly incorporated herein by cross-reference.

In addition to control of the flow to meet the desired deliveredbreathable gas property ranges, it may also be desirable for the patientto control the flow of the apparatus in a manner that allows the flowrate to increase in accordance with a selected rate. Such control mayoffer advantages in acceptance and compliance of such therapy becausethe patient is able to become accustomed to the therapy over a longertime than would be the case without such rate control.

This start-up strategy may be applied for a cold-start or a warm-start.As shown in FIG. 5, an example algorithm monitors the temperature andhumidity delivered at the patient interface (either directly orcalculated from other inputs), for example by means of temperature andhumidity sensors 132 and 134, and ramps up the temperature as quickly aspossible to the desired range (while maintaining relative humidity (RH)within the desired range). Then the flow rate is increased from theinitial value to the desired value in accordance with the user rampsetting such that the delivered temperature and humidity are maintainedwithin the desired ranges.

The algorithm of FIG. 5 may be further described as follows. At 502 ofFIG. 5, the start-up procedure determines if the apparatus is in acool-down mode. If the result is affirmative, the flow rate ismaintained in 504. Otherwise, a minimum flow rate will be set in 506.Process moves to 510 where the flow of the apparatus is controlled tomeet the target or set point. The method then proceeds to 512 where therelative humidity (RH) is measured and compared to a desired range ordeviation of the target or set point for relative humidity. If theresult in 512 is negative then the process proceeds to 514 to controlthe humidity related elements of the apparatus to the set point ortarget for relative humidity. The process then advances to 510 tocontrol the breathable gas flow rate. If the result is affirmative in512 then process advances to 516. In 516, the breathable gas temperatureis checked to see if it is within a desired range or deviation from thetarget or set point value. If the result in 516 is negative then theprocess proceeds to 518 to control the temperature related elements ofthe apparatus to the set point or target for temperature. The processthen advances to 510 to control the breathable gas flow rate.

If the result in 516 is affirmative, then the process proceeds to 520.In 520, the flow rate is checked to see if it is below a desired rangeor acceptable deviation from the therapy target flow rate. If, in 520,the result is negative then the process is complete. If, in 520, theresult is affirmative then the process advances to 522. In 522, the flowrate is measured or calculated to determine if a step increase in therate is appropriate for ramping up of the flow rate. If the stepincrease would raise the flow rate above the therapy target, thenprocess flows to 524 and 510 without an increase in the target set pointof the flow rate for the warm-up process. If in 522 a step increasewould not raise the flow rate above the therapy target, the target setpoint is incremented to increase or ramp up the flow rate in 526 andthen controlled in 510 at the new stepped-up flow rate. In this way, theramping of flow rate may be governed without allowing the humidity ortemperature to deviate from their desired or target set-points.

Another example start-up procedure algorithm is illustrated in FIG. 6.At 602 the start up procedure begins. In 604, the temperature (and/orhumidity) of one or more heating elements (e.g., humidifier heatingelement) is set and allowed to raise to the desired set point asdetermined by a temperature and/or relative humidity sensor. Once theset temperature and/or humidity setting has been reached, at 606, aramp-up procedure for the flow generator begins in which an incrementalincrease in the flow rate will be set over toward a maximum, such as bysetting an incremental increase in the RPM set point of the blower everyseveral minutes. At 608, the temperature and/or humidity levels arechecked with the appropriate sensors to determine if the temperature andhumidity is within an acceptable deviation margin of the set point afteran increase in the blower flow rate. If the margins are acceptable(e.g., a margin of +/−1, 2, 3, 4 or 5 degrees of the temperature settingor +/−1, 2, 3, 4 or 5% relative humidity of the humidity setting) theprocess will flow to 609 to check if the ramp-up of flow has reached thetarget therapy level for the treatment session. If not, then the processreturns to 606 to again increment the flow generator according to theramp-up procedure and its time adjustment period. If, in 609, thetherapy level has been reached, the warm-up process is complete and thetherapy session protocol may begin.

However, in 608, if the levels are not within a predetermined margin ofthe set points, the measurement/comparison process flows to 610 to waita period of time. Process then returns to the comparison process of 608to again check the temperature and/or humidity sensors for compliancewith the deviation margin. In this way, the flow rate of the apparatusmay ramp up in a comfortable fashion to the therapy flow rate settingwhile maintaining the desired set points for the humidity and/ortemperature of the gas delivered by the apparatus.

5.6.1 Re-Ramp Methodology

In some situations, during the course of therapy with the apparatus apatient may desire a temporary decrease in the flow rate to permit thepatient to more comfortably fall asleep with a lower flow rate beforethe flow rate would then return to a higher prescription or therapeuticlevel during sleep. Thus, in some embodiments of the apparatus, are-ramp methodology may be implemented by the controller. The apparatusmay permit the user to activate the re-ramp procedure by a switch,button, knob or other user interface of the apparatus. Thus, uponactivation of the procedure, the apparatus would lower the flow rate fora predetermined period of time. The period of time may optionally beadjustable by the user with an input device of the apparatus. At theconclusion of the period of time the flow rate may then return to thetherapeutic level. Alternatively, it may gradually return to thetherapeutic level over the period of time or after a period of time.However, in the event that humidification is also provided during theparticular therapy session, additional elements of the control of there-ramp procedure may be implemented as a function of the presence ofhumidification and/or heating so as to assist with avoiding rainout orcondensation.

For example, in a typical embodiment, the re-ramp algorithm ormethodology of the apparatus may only permit the re-ramp feature to beactivated after the apparatus has achieved a warmed-up state, such as ifthe apparatus has already completed the warm-up procedure previouslydescribed. Similarly, in an embodiment, the re-ramp feature may bedisabled if the apparatus has achieved a cool down state such as at atime after completing a cool-down methodology or when the apparatus isperforming a cool-down methodology as described in more detail herein.Thus, the methodology of the re-ramp feature may be implemented as afunction of humidification and/or temperature or a humidification stateand/or temperature state of the apparatus. In the event that a cool-downstate has been achieved, such as with the following described cool-downmethodology, and/or the re-ramp feature is disabled, the apparatus maythen be re-activated by execution of the warm-up methodology previouslydescribed rather than the re-ramp procedure.

In some embodiments, the selection of the rate for the reduced flowduring the re-ramp procedure may be user adjusted or selected with aninput device or user interface of the apparatus. Additionally, in someembodiments the reduced flow rate may be a function of humidity and/ortemperature such that the reduced flow rate selection is at leastpartially set in a manner that prevents condensation from forming in thepatient interface and/or delivery tube. For example, the algorithm maymonitor the temperature and humidity internal and/or external to theapparatus, for example by means of temperature and humidity sensors, andthen automatically select a reduced flow rate, such as from a look-uptable based on the temperature and/or humidity information.

In some embodiments, the reduced flow may be implemented without ablower speed change by the flow generator. In such an embodiment, anexhaust vent or release valve, which may be a mechanical valve that iscontrolled by a processor or controller of the apparatus, may be openedto vent part of a humidified gas supply from the blower so that only aportion of the humidified flow generated by the flow generator isdirected to the patient interface. In this way, a lower humidified flowrate may be delivered to the patient for the re-ramp procedure. The ventor release valve may then close, such as gradually over a period of timethat is typically longer than several breaths, to return the humidifiedflow to the therapeutic rate. Although not shown in FIG. 1, such arelease valve or exhaust vent may, for example, be positioned to exhaustgas flow generated by the blower 104 at a position in the air delivercircuit after the humidifier 112.

5.7 Cool-Down Methodology

Another consequence of the practical consideration described above isthat the immediate power-down of the apparatus may lead to condensationin the apparatus—particularly the tube—because the heated water masswill continue to emit vapor and so the regions where the breathable gaspath is in thermal contact with the environment, for example the tubewalls, may cool rapidly. The presence of condensation in the apparatuswill adversely affect the comfort and/or function of the apparatus at asubsequent start-up, because droplets may be blown down the tube to thepatient interface causing patient discomfort, and/or the presence ofwater in the heated tube may lead to additional humidification in thebreathable gas delivered to the patient or otherwise affect the abilityof the system to control the breathable gas delivery at the patientinterface within the desired ranges.

An aspect of the current technology is a control methodology that may beoptionally used with the apparatus to control the rate of cooling of theapparatus—especially the tube—to diminish the likelihood of significantcondensation forming during apparatus power-down.

Such a strategy includes implementing a sequence of apparatus states ortransitions to promote the maintenance of the temperature of thebreathable gas in the system above the local dew-point temperature.Optionally, this sequence may be initiated conditionally upon, and/ortriggered by, detection of the absence of a patient connected to theapparatus. Such detection may be by detection of fluctuations inpressure and/or flow signal(s). The initiation of this sequence may bedelayed by a predetermined period, which may be patient-selectable,following such triggering, to allow for temporary disconnection andreconnection of the apparatus. The predetermined period may be about1-30 minutes.

This strategy can be accomplished by the example logic described in FIG.7. The flow rate Fmin1 may be about 50%-150% of the typical therapyflow. The flow rate needs to be sufficiently high to promote cooling ofthe water mass but not so high so as to generate obtrusive noise. Thisflow rate may be a fixed value, a value that is directly or indirectlyselected by the user, for example should a rapid cool-down be desired,and/or a variable value that follows a profile with time, or with asensed breathable gas property value such as humidity.

The flow rate Fmin2 is a small flow of about 5%-35% of the typicaltherapy flow—sufficiently large to transport the breathable gas to allowsensing and control, but sufficiently small that the humidification ofthe breathable gas is low and does not cause condensation when theapparatus is subsequently powered-down. The transition in flow rate fromFmin1 to Fmin2 may be controlled to a predetermined profile. Fmin2 maybe a fixed value, a value that is directly or indirectly selected by theuser, for example should a rapid cool-down be desired, and/or a variablevalue that follows a profile with time, or with a sensed breathable gasproperty value such as humidity.

This cool-down strategy applies to any mode or phase of operation of theapparatus. Optionally, a pause to therapy may be requested by the usersuch that the breathable gas conditions are maintained for a shortperiod, for example 1-30 minutes, and if therapy is not restarted withinthis period, either manually or by the detection method above, then thecool-down strategy will be initiated. As shown in FIG. 7, the algorithmmonitors the temperature and humidity delivered at the patient interface(either directly or calculated from other inputs), for example by meansof temperature and humidity sensors 132 and 134, and ramps down thehumidity as quickly as possible until such time as the system humidityis stable, whilst maintaining an acceptable dew-point margin, forexample about a 2-5° C. margin. The margin can be determined from theSaturation Vapour Pressure at the flow temperature, for example usingthe formulas in ISO Standard 8185 2007. The flow rate is decreased fromthe initial value to the Fmin2 in a manner that allows the maintenanceof the dew-point margin. The apparatus may then be powered-down.

The algorithm of FIG. 7 may be summarized as follows. In 702, after thetreatment therapy controlled by the apparatus is stopped, humiditygeneration with the humidifier is stopped. In 704, the flow rategenerated by the flow generator is controlled to the Fmin1 target value.In 706, one or more of the heating elements are controlled to maintain atarget temperature in the delivery tube of the patient interface. In708, a dew-point temperature is checked to assess if it has stabilized.If it has not, process flow returns to 704. If it has, process flows to710. In 710, the flow rate of the flow generator is then controlled tothe target Fmin2 value. In 712, one or more of the heating elements arecontrolled to maintain a target temperature in the delivery tube of thepatient interface. In 714, a dew-point temperature is checked to assessif it has stabilized. If it has not, process flow returns to 710. If ithas, process flow of the cool-down procedure is complete.

5.8 Applications of Method and Apparatus

A user will be titrated to determine the optimal flow rate andtemperature for treating the user's sleep disordered breathing (SDB).The optimal settings for flow rate and temperature are those thatmaximize efficacy of the therapy as well as user comfort. For example,the temperature will be set to the highest value within the rangecapable by the device that is deemed comfortable by the user. Thetemperature may also be changed to compensate for any droplets of waterthat may form in the air delivery tube or user interface, for examplenasal cannula. The temperature may also be changed to maximize theefficacy of the therapy. For flow, an example would be for the rate offlow to start at the lowest possible by the device. When the user isasleep and SDB events are detected, such as by the controller of thedevice, the flow rate would be incrementally increased in response tothe SDB events (for example, apneas, hypopneas, flow limitation andsnoring) to prevent them from repeating and hence maximizing theefficacy of the therapy. Another method would be to set the flow rate tothe highest rate that is comfortable for the user when awake. When theuser is asleep, the necessary changes in flow rate may be made inresponse to the SDB events, again to maximize the efficacy of thetherapy.

Changes to flow rates and temperature may be done manually, by anobserver of the user when they are asleep. For example, by a sleeptechnologist observing the user using polysomnography (PSG).

Changes to flow rate, gas temperature and/or humidity levels may alsooccur automatically in response to the SDB events detected by theapparatus. This would be based on an algorithm that incrementallyincreases the flow rate, gas temperature and/or humidity levels inresponse to the SDB events. The magnitude of the increase would begoverned by the type of the SDB event. For example, the increase in flowrate, gas temperature and/or humidity levels would be greater for anapnea compared to flow limitation which in turn would be greater thanthe response to snore. Alternatively, incremental decreases in the flowrate, gas temperature and/or humidity levels would occur in response toan absence of detected SDB events after a certain period of time.

The settings of flow rate, humidity and/or temperature may be increasedor decreased by the device with some step value by simply detectingwhether any one or more of these SDB events occur. Moreover, suchadjustments may be a function of the measure of the detected SDB event.For example, a measure of partial obstruction may be a varying indexfrom 0 to 1 where 1 is fully obstructed, 0 is not obstructed and 0.5 ifhalf obstructed. The change in any of the flow rate, humidity and/ortemperature may then be a function of the degree of partial obstruction,such as, a function that generates a greater adjustment when there is alarger degree of obstruction and a lesser adjustment when there is asmaller degree of obstruction. In some embodiments, a degree of partialobstruction may be assessed by a flattening analysis of a respiratoryflow signal, a roundness analysis of a respiratory flow signal and/orother partial obstruction methodology for assessing of the patient'supper airway.

To assist in the treatment of SDB, in some embodiments the ratio of theouter diameter of the nasal prongs of the patient interface to thesurface area of user's nares may be increased or decreased. Thesechanges would be to increase the efficacy and comfort of the therapy.

Once titration has been effected, optionally, the patient may alter thetherapy settings manually within a restricted range to improve comfortaccording to personal choice.

5.9 Cycling

In some embodiments of the technology, the flow and or humidification ofair delivered to each nare is individually controlled. For example, ahigher flow and/or more humidification may be delivered on one sidecompared to the other. In one form, each of the air flow &humidification may be individually cycled in a nare. For example, a flowrate may be adjusted in one nare while maintaining a fairly constantflow rate or humidity in the other nare. By way of further example, ahigh flow rate may alternate between the left nare and a right nare suchthat when a high rate is directed at one nare, a low rate is directed atthe other. In another form changes in flow and/or humidification of airdelivered to one nare are synchronized with changes in flow and orhumidification of air delivered to the other nare.

The delivery of a higher flow to one nare compared to the other may beto compensate for a user with unilateral nasal obstruction. In oneembodiment, the higher flow rate would be delivered to the nare that wasnot obstructed. This would maximize the efficacy of the therapy.Alternatively, a higher rate may be delivered to the obstructed nare asan attempt to decrease the obstruction. Obstruction may be determined byautomatic method of detecting partial obstruction, for example, byanalysis of a respiratory flow signal. Such an analysis may beindependent for the respiratory flow signal associated with each nare.Alternatively, unilateral partial obstruction may be detected by anincrease in a measure of pressure from a pressure sensor associated withone nare with respect to a measure of pressure of another pressuresensor associated with the other nare.

The delivery of more humidification to one nare compared to the othermight be to compensate for the higher flow being delivered to one narebecause it is less obstructed. Alternatively, more humidification may bedelivered to the nare with higher nasal resistance to reduce thisresistance. Optionally, while this is occurring, a higher flow may bedelivered to the other nare. After the higher nasal resistance isreduced, by more humidification and/or a higher flow rate, and theresistance is equal between the two nares, the humidification and airflow may then be returned to equal delivery to each of the nares. Thismay be tested by analysis of the relative pressures of the sensorsassociated with each nare. For example, the flows directed at each naremay be set to be equal and the two pressures associated with the naresmay then be checked and compared for substantial equality, which mayindicate that there is no unilateral obstruction.

This delivery of different flow can be achieved, for example, by the useof two motors within the device. One motor for each of the two nareswith a controller linking both motors. Alternatively, a single motorblower might be used with controlled venting valves in the flow pathsfor each nare. In such a case, the blower may be set to a desired ratefor the highest flow desired for either nare. The flow at the high ratemay be delivered to one nare without substantial venting while theblower flow rate to the other nare may be reduced by venting some of theflow of the flow path of the other nare without delivering all of it tothat nare. This may be achieved by separately controlling the diameterof an aperture associated with a venting valve of each delivery tubeassociated with each nare by the controller. Alternatively, one or morevariably controlled gate valves may split a single supply tube from ablower into a y-junction. For example, mechanical gate valves, near ay-junction, may then be set to position(s) to gate a portion of the flowto one delivery tube directed at one nare and a portion of flow intoanother delivery tube directed at the other nare. For example, 60% ofthe flow may be directed to one nare and 40% of the flow may be directedat the other nare. The gate valve may be controlled to divide the supplyrate by other percentages (e.g., 50%/50%, 0%/100% etc.) Essentially, thecontroller can set the gate valve to divide the flow between the naresby any desired position or aperture setting. An example of suitable gatevalves may be comparable to the gate valves illustrated in FIG. 2A or 2Bbut with the flows traveling in the opposite direction from thatillustrated in those figures. Optionally, additional tubes and gatevalves may also be added to then adjust the humidity levels directed toeach nare tube as previously described with regard to FIGS. 2A and 2B.

Still further, the delivery of different levels of humidification can beachieved, for example, by altering the proportion of air being deliveredthat comes from the humidifier compared to that from the environment. Byincreasing the proportion of air from the environment the lower theamount of humidification being delivered to the patient. In such a case,ambient humidification and temperature sensors may be utilized toprovide the controller with data concerning these ambient conditions.Alternatively, there may be two humidification systems. One for eachnare of the user with a controller linking both humidifiers.

5.10 Dual Rate Operation

In one embodiment of the technology, a dual rate mode of operation maybe employed. In this mode, the device is triggered by the inspirationalflow of a user, in particular by the flow rate provided at the beginningof inspiration. This flow rate may be detected by inference from thepressure signal, or otherwise, and compared to a predeterminedthreshold. The threshold may be set to different sensitivities, e.g.high, medium and low. Once a trigger event is detected, a first flowrate is provided. When the inspirational flow of a user, in particularby the flow rate provided at the end of inspiration, falls below anotherthreshold, the device cycles to a second flow rate. The flow rate may bedetected as described above. Again, the thresholds for cycling may beset to different sensitivities, e.g. high, medium and low.

In one form of this dual rate operation, the inspiration flow rate ishigher than the expiration flow rate. This is a form of expiration flowrelief that may improve the comfort of the therapy.

In another form of this dual rate operation, the expiration flow rate ishigher than the inspiration flow rate. This may assist in furtherincreasing the end expiratory pressure (EEP) in the upper airway of theuser. By increasing the EEP, the efficacy of the therapy may beimproved.

As previously mentioned, such triggering may also be utilized toimplement first and second distinct humidification levels or first andsecond distinct breathable gas temperatures according to the detectedphases of the patient's respiratory cycle. Thus, the controller may setdifferent gas temperatures and/or different humidification levelsdepending on the phase of respiration.

5.11 Alternative Therapy

The therapeutic mode described herein, may be implemented in a devicealso capable of delivering CPAP or APAP therapy. In this case, the modeof therapy delivered by the device may be changed through a button,dial, menu or other control. A change of therapeutic mode might also beassociated with changing the air-delivery circuit to that appropriate tothe therapeutic mode.

The device may have an indicator, for example an LED, which willilluminate when the device believes it is not satisfactorily treatingthe SDB of the user based on data logging. For example, the LED would beilluminated when the device recorded SDB events were above apredetermined threshold at the end of a session. This threshold could beset based on the requirements of the treating physician. An example of athreshold would be an apnea and hypopnea index (AHI) greater than 5 perhour of use. The illumination of this indicator based on SDB eventswould indicate a change to an alternative therapy from that described inthis patent to conventional continuous positive airway pressure (CPAP)or automatic positive airway pressure (APAP).

The indicator described above in one case may result in the device ofthe user being changed to a CPAP/APAP device. In another case, it mayindicate that the mode of therapy being delivered by the device beswitched, manually, to CPAP/APAP mode. For this the device would becapable of delivering both types of therapy (i.e., that described inthis document and CPAP/APAP). In another case, the indicator may lead toan automatic change of therapy mode and the device which is capable ofdelivering both types of therapy automatically makes the change. Theindicator in this instance would be to notify the user that the changehad occurred.

5.12 Dislodgement Avoidance and Detection

The relatively high flow rates of the devices and systems may give riseto additional problems relating to patients experiencing problemswherein the nasal cannula are accidently dislodged during operation.These problems may include potential damage to the eyes or face of thepatient wherein the high flow rates of air are accidently directed tosensitive parts of the face.

The preferred system and device may also detect accidental dislodgement,wherein the dislodgement is detected by at least one of theaforementioned preferred sensors. When the dislodgement is detected, thesystem or device may be automatically shut off to prevent or limitpotential damage from the high flow rates being accidentally directed tosensitive parts of the patient's face. Alternatively or in addition tothe shut off, the dislodgment detection may automatically open amechanical vent valve controlled by the controller to vent the air at ornear the controller or flow generator in a manner that more immediatelydepressurizes the supply tube to the cannula. One example dislodgementsensor may be a pressure transducer that detects a change in pressure asan indication of dislodgement. In another example, a clip withelectrical contacts 1210A, 1210B, such as that illustrated in FIG. 12 or13, may serve as a dislodgment sensor by sending an electrical switchsignal to the controller. During use, the clip may be attached to aportion of the nares, such as at the base of the nose. A light springforce used to hold the clip in place may also be utilized to activatethe sensor upon dislodgment. Upon removal or dislodgment, the clip maybe configured to spring closed (or open depending on its desiredconfiguration). The closing of the contacts (or opening thereofdepending on the configuration of the switch and the spring action) maythen be detected electrically by the controller as a dislodgment. Theclip may even be combined with the other components of the patientinterface such as the nasal dilators previously discussed (e.g., thedilator of FIG. 8 or 11), and may even also serve to maintain thecannula in place as described further herein.

In this regard, the chance or likelihood of accidental dislodgement mayalso be minimized by attaching a specialized clip 1310 onto the nasalcannula. The clip may be constructed of flexible and resilient material(including polyermic materials) and may attach and secure the nares ofthe patient to the nasal cannula with a retaining force, and may stillmaintain a non-sealed relationship between the nose and nasal cannula.

Also in some embodiments, the end of the nasal cannula that may beinserted into the nose during operation may include an air diffuser suchas the example diffuser with radial fins 1440 on the prong 880illustrated in FIG. 14. Preferably, the air diffuser may prevent orlimit the flow of air in a single direction but increases the dispersionof air exiting the nasal cannula. This may serve as an additional safetyfeature, wherein the nasal cannula are accidentally dislodged from theirposition in nares. If the dislodgement occurs, the air diffuser reducesthe risk that relatively high flow air will directed into a sensitiveregion of the patient's face such as the eyes. Even if the air isaccidentally directed into the eyes of the patient, the attachment ofthe air diffuser may significantly reduce the overall flow of airdirected into the eyes and thereby increase safety of the device andreduce the overall risks.

In situations where the nasal cannala is dislodged while in operation,and this is detected by sensors attached to the system, the system ordevice may include a controller that sounds and/or displays an alarm toalert a patient or clinician to the dislodgement.

5.13 Cannula Design Modification

The nasal cannula previously described for use with any of theaforementioned embodiments may further include noise limiting features.These noise limiting features may reduce the overall noise heard by thepatient and people around the patient, wherein the system or device isoperational.

In some embodiments, these noise limiting features may includespecialized baffles mounted on or in the nasal cannula or prongs todisperse or diffuse any noise emitted by the nasal cannala. This may beparticularly true when the nasal cannula are delivering relatively highflow rates when compared to standard closed CPAP devices.

The noise baffle may be constructed of a foam insert, a maze-likestructure mounted on or proximal to the end of nasal cannula engagingthe nares of the patient. An example, baffle 1550 about a prong 880 isillustrated in FIG. 15.

In the foregoing description and in the accompanying drawings, specificterminology, equations and drawing symbols are set forth to provide athorough understanding of the present technology. In some instances, theterminology and symbols may imply specific details that are not requiredto practice the technology. Moreover, although the technology herein hasbeen described with reference to particular embodiments, it is to beunderstood that these embodiments are merely illustrative of theprinciples and applications of the technology. It is therefore to beunderstood that numerous modifications may be made to the illustrativeembodiments and that other arrangements may be devised without departingfrom the spirit and scope of the technology. For example, a device inaccordance with the present technology could provide nasal CPAP. In oneform of the technology, drug delivery is provided with the supply ofbreathable gas, for example in the form of a nebulised drug. Forexample, the present system may be used for treatment of COPD or CysticFibrosis and accompanied with appropriate drugs for the respectivediseases.

1-97. (canceled)
 98. A system for providing high flow respiratorytherapy to a patient, the system comprising: a nasal interfaceconfigured to deliver a flow of pressurized breathable gas to thepatient, the nasal interface comprising: a pair of nasal inserts to beinserted into the nares of the patient without sealing against thenares; and an inlet through which the pressurized breathable gas isreceived; a conduit to provide the flow of pressurized breathable gas tothe nasal interface, the conduit comprising: a distal end portionconfigured to be connected to a supply of pressurized breathable gas; aproximal end portion configured to be connected to the inlet of thenasal interface; a tube heating element to heat gas within the conduit;and a set of conduit sensors located at the proximal end portion of theconduit, the set of conduit sensors comprising (i) a first temperaturesensor to generate a first temperature signal indicating a temperatureof the gas within the conduit and (ii) a first humidity sensor togenerate a first humidity signal indicating a level of humidification inthe gas within the conduit; and a respiratory treatment device togenerate the flow of pressurized breathable gas to provide high flowrespiratory therapy to the patient, the respiratory treatment devicecomprising: a housing; a blower positioned within the housing to drawair from an ambient environment around the housing and to generate apressurized flow of gas; a set of device sensors located proximate tothe blower within the housing, the set of device sensors comprising (i)a second temperature sensor to generate a second temperature signalindicating a temperature of the pressurized flow of gas and (ii) a flowsensor to generate a flow signal indicating a flow rate for thepressurized flow of gas; a humidifier to humidify the pressurized flowof gas, the humidifier comprising (i) an inlet to receive thepressurized flow of gas, (ii) a water reservoir to hold a volume ofwater and through which the pressurized flow of gas passes to addhumidification, (iii) a heater to warm the water contained in the waterreservoir, and (iv) an outlet through which the pressurized flow of gaswith humidification is output as the pressurized breathable gas to bedelivered to the patient via the conduit and the nasal interface; and acontroller to control operation of, at least, the blower, the heater,and the tube heating element to provide high flow therapy to thepatient, the controller being configured to control the operation of theblower, the heater, and the tube heating element based on, at least, thefirst temperature signal, the first humidity signal, the secondtemperature signal, and the flow signal.
 99. The system of claim 98,wherein the respiratory therapy device further comprises: an air inletin the housing through which the blower draws the air from the ambientenvironment; and a gas supply that is coupled to the air inlet to mixsupplemental gas provided via the gas supply with the air from theambient environment.
 100. The system of claim 99, wherein thesupplemental gas comprises oxygen.
 101. The system of claim 98, whereinthe controller controls operation of, at least, the blower, the heater,and the tube heating element so that a humidification range for thepressurized breathable gas provided to the patient includes up to 100%humidification.
 102. The system of claim 98, wherein the controllercontrols operation of, at least, the blower, the heater, and the tubeheating element so that a range of flow rates for the pressurizedbreathable gas provided to the patient includes up to 50 liters/minute.103. The system of claim 98, wherein the controller controls operationof, at least, the blower, the heater, and the tube heating element sothat a range of flow rates for the pressurized breathable gas providedto the patient includes a top flow rate that exceeds 50 liters/minute.104. The system of claim 98, wherein: the controller controls operationof, at least, the blower, the heater, and the tube heating element sothat a humidification range for the pressurized breathable gas providedto the patient includes up to 100% humidification, and the controllercontrols operation of, at least, the blower, the heater, and the tubeheating element so that a range of flow rates for the pressurizedbreathable gas provided to the patient includes up to 50 liters/minute.105. The system of claim 98, wherein: the controller controls operationof, at least, the blower, the heater, and the tube heating element sothat a humidification range for the pressurized breathable gas providedto the patient includes up to 100% humidification, and the controllercontrols operation of, at least, the blower, the heater, and the tubeheating element so that a range of flow rates for the pressurizedbreathable gas provided to the patient includes a top flow rate thatexceeds 50 liters/minute.
 106. The system of claim 98, wherein therespiratory treatment device further comprises: another set of devicesensors that are positioned downstream of the humidifier, the other setof device sensors generating post-humidification signals that indicateone or more conditions of the pressurized breathable gas output by thehumidifier, wherein the controller is further configured to controloperation of, at least, the blower, the heater, and the tube heatingelement additionally based on, at least, the post-humidificationsignals.
 107. The system of claim 106, wherein: the other set of devicesensors comprise a third temperature sensor to generate a thirdtemperature signal indicating a temperature of the pressurizedbreathable gas output by the humidifier, and the third temperaturesignal is part of the post-humidification signals that are used by thecontroller to control operation of, at least, the blower, the heater,and the tube heating element.
 108. The system of claim 106, wherein: theother set of device sensors comprise a second humidity sensor togenerate a second humidity signal indicating a level of humidificationfor the pressurized breathable gas output by the humidifier, and thesecond humidity signal is part of the post-humidification signals thatare used by the controller to control operation of, at least, theblower, the heater, and the tube heating element.
 109. The system ofclaim 106, wherein: the other set of device sensors comprise (i) a thirdtemperature sensor to generate a third temperature signal indicating atemperature of the pressurized breathable gas output by the humidifierand (ii) a second humidity sensor to generate a second humidity signalindicating a level of humidification for the pressurized breathable gasoutput by the humidifier, the third temperature signal is part of thepost-humidification signals that are used by the controller to controloperation of, at least, the blower, the heater, and the tube heatingelement, and the second humidity signal is part of thepost-humidification signals that are used by the controller to controloperation of, at least, the blower, the heater, and the tube heatingelement.
 110. The system of claim 98, wherein: the set of device sensorsfurther comprise a second humidity sensor to generate a second humiditysignal indicating a level of humidification for the pressurized flow ofgas, and the controller is further configured to control operation of,at least, the blower, the heater, and the tube heating elementadditionally based on, at least, the second humidity signal.
 111. Thesystem of claim 98, wherein: the set of device sensors further comprisea pressure sensor to generate a pressure signal indicating a level ofpressure for the pressurized flow of gas, and the controller is furtherconfigured to control operation of, at least, the blower, the heater,and the tube heating element additionally based on, at least, thepressure signal.
 112. The system of claim 98, wherein: the set of devicesensors further comprise (i) a second humidity sensor to generate asecond humidity signal indicating a level of humidification for thepressurized flow of gas and (ii) a pressure sensor to generate apressure signal indicating a level of pressure for the pressurized flowof gas, and the controller is further configured to control operationof, at least, the blower, the heater, and the tube heating elementadditionally based on, at least, the second humidity signal and thepressure signal.
 113. The system of claim 98, wherein: the set ofconduit sensors further comprise a pressure sensor to generate apressure signal indicating a level of pressure for the pressurizedbreathable gas within the conduit, and the controller is furtherconfigured to control operation of, at least, the blower, the heater,and the tube heating element additionally based on, at least, thepressure signal.
 114. The system of claim 98, wherein the respiratorytherapy device further comprises: a third temperature sensor positionedat or around the heater to generate a third temperature signalindicating a temperature of the heater, wherein the controller isfurther configured to control operation of, at least, the heateradditionally based on, at least, the third temperature signal.
 115. Thesystem of claim 98, wherein the conduit is fluidly connected torespiratory therapy device to receive the pressurized breathable gasoutput from the humidifier.
 116. The system of claim 98, wherein: thenasal interface further comprises: a nasal interface body with one ormore surfaces defining one or more fluid passageways from the inlet tothe pair of nasal inserts; a left lateral headgear connector extendingfrom a left lateral side of the nasal interface, the left lateralheadgear connector including a left front surface that defines a leftaperture that extends at least partially through the left lateralheadgear connector; and a right lateral headgear connector extendingfrom a right lateral side of the nasal interface, the right lateralheadgear connector including a right front surface that defines a rightaperture that extends at least partially through the right lateralheadgear connector; and the system further comprises: a headgearassembly to position the nasal interface below the patient's nares, theheadgear assembly comprising a plurality of headgear straps that includeat least: a left headgear strap with a left end that is configured toconnect to the left lateral headgear connector, wherein the left end ofthe left headgear strap includes a left projection that extendsorthogonally from a surface of the left end, wherein the left projectionis configured to extend through and engage the left aperture to connectthe left headgear strap to the left lateral headgear connector; and aright headgear strap with a left end that is configured to connect tothe right lateral headgear connector, wherein the right end of the rightheadgear strap includes a right projection that extends orthogonallyfrom a surface of the right end, wherein the right projection isconfigured to extend through and engage the right aperture to connectthe right headgear strap to the right lateral headgear connector. 117.The system of claim 116, wherein the left projection extends through theleft front surface of the left lateral headgear connector when the leftheadgear strap is connected to the left lateral headgear connector, andwherein the right projection extends through the right front surface ofthe right lateral headgear connector when the right headgear strap isconnected to the right eft lateral headgear connector.
 118. The systemof claim 116, wherein engagement of the left aperture and the leftprojection provides a connection between the left headgear strap and theleft lateral headgear connector without loose strap ends around or nearthe patient's face, and wherein engagement of the right aperture and theright projection provides a connection between the right headgear strapand the right lateral headgear connector without loose strap ends aroundor near the patient's face.
 119. The system of claim 118, wherein theleft lateral headgear connector and the right lateral headgear connectorare made of a flexible material.
 120. The system of claim 119, whereinthe left lateral headgear connector is configured to lay against andconform to a left side of the patient's upper lip and cheek when thenasal interface is in use, and wherein the right lateral headgearconnector is configured to lay against and conform to a right side ofthe patient's upper lip and cheek when the nasal interface is in use.121. The system of claim 116, wherein the left headgear strap isconfigured to extend along the patient's left cheek, above the patient'sleft ear, and to a back of the patient's head, wherein the rightheadgear strap is configured to extend along the patient's right cheek,above the patient's right ear, and to the back of the patient's head,and wherein the left headgear strap and the right headgear strap areconnected to each other at a location corresponding to the back of thepatient's head.
 122. The system of claim 116, wherein the inlet ispositioned on a lateral side of the nasal interface body such that, whenconnected, the conduit extends from the lateral side of the nasalinterface.
 123. The system of claim 116, wherein the nasal interfacebody includes a first barrel portion and a second barrel portion,wherein the first barrel portion is provided on a frame that includesthe left lateral headgear connector and the right lateral headgearconnector, wherein the second barrel portion includes the inlet and isconfigured to sealingly connect to the first barrel portion.
 124. Thesystem of claim 123, wherein the first barrel portion includes an uppersurface and a mounting boss extending downward from the upper surfaceand connecting to the frame at a position below the upper surface,wherein the mounting boss, the upper surface, and the frame define aloop into which the second barrel portion is configured to be inserted.125. The system of claim 98, further comprising means for connecting theinlet to the conduit.
 126. The system of claim 98, further comprisingmeans for connecting the conduit to the respiratory therapy device. 127.The nasal mask assembly of claim 98, further comprising meanstransporting the respiratory therapy device and supporting therespiratory therapy device during operation.